Investigators recorded more than 5,000 hours of conversations of John Gotti’s son-in-law and his associates in the scrap-metal industry as part of their massive racketeering case against him, The Post has learned.

Sources said cops for more than two years bugged business phones and cell phones belonging to Carmine Agnello and several of his closest friends involved in the auto-salvage and scrap-metal businesses centered on Liberty Avenue in Queens.

The wiretaps — part of a probe into stolen car parts — were separate from the volume of recordings made by undercover NYPD cops and probers from the office of Queens District Attorney Richard Brown during an 18-month sting operation.

In that investigation, undercover cops set up a bogus auto-salvage business near Shea Stadium and began selling metal to a competitor of Agnello’s metal-shredding business.

The undercover cops were amazed when Agnello — whose company, New York Shredding, does $30 million a year in business and handles 80 percent of the scrap-yard crushing in the area — walked in one day.

“You’re doing business with me,” he allegedly told them, demanding they sell the scrap to his company.

Agnello, 40, was captured on tape in the sting threatening his rivals unless they caved in to his demands — and also instructing a henchman how to make a Molotov cocktail to torch the business.

Agnello was initially hit with state racketeering charges by DA Brown. Federal prosecutors a few months later superseded the DA’s case with a federal racketeering indictment that included arson, extortion and tax-fraud charges.

In all, the feds charged seven defendants, including Agnello’s bookkeeper and his brother.

The indictment accused Carmine Agnello of being a member of the Gambino crime family his father-in-law is reputed to run — and heading his own ring that strong-armed not only a rival scrap-metal business, but a stock broker between 1996 and 2000.

Agnello, who is being held on $11 million bail, has denied all charges. His attorney, Jay Goldberg, declined comment.

Agnello, who is married to Gotti’s daughter, Victoria, faces up to 25 years in prison, if convicted.